FSM_Linked_List

//============================================================================
// Name        : FSM_Test.cpp
// Author      : uMinded
// Version     : 0.1
// Description : FSM using linked lists
// Props       : Matthieu M. on StackOverflow
//============================================================================

#include <stdio.h>
#include <stdlib.h>

struct Event
{
    Event(const char* a, const char* n):
        action(a), name(n) {}

    const char* action;
    const char* name;
    void (*func)(Event);
};

struct StateNode;
struct State
{
    State(const char* n):
        me(0), name(n) {}

    StateNode* me;
    const char* name;
    void (*in_func)(State);
    void (*out_func)(State);
};

struct StateNode
{
    StateNode(Event e, State& s, StateNode* n):
        event(e), state(s), next(n) {}

    Event event;
    State& state;
    StateNode* next;
};

struct Transition
{
    Transition(State& origin, Event e, State& destination):
        node(e, destination, origin.me) { origin.me = &node; }

    StateNode node;
};

// Global variable to hold the current state
State State_Curr = NULL;

void FSM_Init(State Head)
{
    State_Curr = Head;
    State_Curr.in_func(State_Curr);
}

void FSM_Feed(char event)
{
    StateNode* State_Find = State_Curr.me;
    int found = 0;
    do {
        if( (*State_Find->event.action) == event ) {
            State_Curr.out_func(State_Curr);
            State_Find->event.func(State_Find->event);
            State_Curr = State_Find->state;
            State_Curr.in_func(State_Curr);
            found = 1;
        }
        else if (State_Find->next != NULL) {
            State_Find = State_Find->next;
        }
        else if (State_Find->next == NULL) {
            return;
        }
        else { continue; }
    } while(found == 0);
}

void s_in_print(State state)
{
    printf("Entering State: %s \n", state.name);
}

void s_out_print(State state)
{
    printf("Exiting State:  %s \n", state.name);
}

void e_print(Event event)
{
    printf("Event Recieved: %s \n", event.name);
}

int main ( void )
{
/* ASCII ART!!                *** STATE CHART ***

                                  +---------+
                                  | state1: |
                                  | Welcome |
                                  +---------+

                                     |  ^
                           KEY_DOWN  |  | KEY_UP
                                     V  |

+-------------+                   +---------+                    +--------------+
| state3:     | <--- KEY_LEFT --- | state2: |  <--- KEY_LEFT --- |  state4:     |
| View - Left | --- KEY_RIGHT --- | View    | --- KEY_RIGHT ---> | View - Right |
+-------------+                   +---------+                    +--------------+

                                     |  ^
                           KEY_DOWN  |  | KEY_UP
                                     V  |

+-------------+                   +---------+                    +---------------+
|state6 :     | <--- KEY_LEFT --- | state5: | <--- KEY_LEFT ---  | state7:       |
|Setup - Left | --- KEY_RIGHT --- | Setup   | --- KEY_RIGHT ---> | Setup - Right |
+-------------+                   +---------+                    +---------------+

 */
    State state1("Welcome");
        state1.in_func = &s_in_print;
        state1.out_func = &s_out_print;
    State state2("View");
        state2.in_func = &s_in_print;
        state2.out_func = &s_out_print;
    State state3("View - Left");
        state3.in_func = &s_in_print;
        state3.out_func = &s_out_print;
    State state4("View - Right");
        state4.in_func = &s_in_print;
        state4.out_func = &s_out_print;
    State state5("Setup");
        state5.in_func = &s_in_print;
        state5.out_func = &s_out_print;
    State state6("Setup - Left");
        state6.in_func = &s_in_print;
        state6.out_func = &s_out_print;
    State state7("Setup - Right");
        state7.in_func = &s_in_print;
        state7.out_func = &s_out_print;

    Event KEY_UP("w","UP");
        KEY_UP.func = &e_print;
    Event KEY_DOWN("s","DOWN");
        KEY_DOWN.func = &e_print;
    Event KEY_LEFT("a","LEFT");
        KEY_LEFT.func = &e_print;
    Event KEY_RIGHT("d","RIGHT");
        KEY_RIGHT.func = &e_print;

    Transition t0(state1, KEY_DOWN, state2);

    Transition t1(state2, KEY_LEFT, state3);
    Transition t2(state3, KEY_RIGHT, state2);
    Transition t3(state2, KEY_RIGHT, state4);
    Transition t4(state4, KEY_LEFT, state2);
    Transition t5(state2, KEY_UP, state1);
    Transition t6(state2, KEY_DOWN, state5);

    Transition t7(state5, KEY_LEFT, state6);
    Transition t8(state6, KEY_RIGHT, state5);
    Transition t9(state5, KEY_RIGHT, state7);
    Transition t10(state7, KEY_LEFT, state5);
    Transition t11(state5, KEY_UP, state2);

    printf("Example FSM using linked lists \n");
    printf("To navigate use 'wads' & 'x' to exit \n\n");

    char feed = '0';
    FSM_Init(state1);
    while((feed = getchar()) != 'x') // Press 'x' to exit program!
    {
        FSM_Feed(feed);
    }

  return(0);
};